Improve Chapter 31 resources lesson

[jules-tth]

Scope

• Replaces the generic organizations/conferences/resources lesson with a practical Linux-operator guide.
• Covers primary-source selection, standards/community organizations, conferences, online communities, resource evaluation, safety around copied commands, evidence commands, a personal operations library, lab practice, and review questions.

Verification

• python -m pip install -r requirements.txt could not run because python is not on PATH.
• python3 -m pip install -r requirements.txt passed.
• python3 -m mkdocs build --strict passed.
• make build passed.
• git diff --check passed.
• find docs -type f -name "*.md" -size 0 -print returned no files.
• No dedicated repo-local link-check script was found beyond MkDocs/Makefile build paths.

Duplicate-prevention check

Open PRs from jules-tth already cover Chapter 31 through 31.9; final pre-PR target-file overlap query returned no open PR touching docs/lessons/31_methodology_policy_and_politics/31.10_organizations,_conferences,_and_other_resources.md.

[jules-tth]

Reviewer assignment to bdorlus failed during PR creation: GraphQL: jules-tth does not have the correct permissions to execute RequestReviewsByLogin (requestReviewsByLogin).